An Overview of Irregularly Spelled Words

To become fluent readers, students need to recognize lots of words instantaneously, without sounding them out. Students tend to start this process of sight recognition by learning high-frequency words, or the words that appear most often in reading. Those include words like a, the, and of.

Many teachers learned that students should memorize high-frequency words as whole words. This approach requires students to visually memorize hundreds of words, which can be overwhelming. Experts now recommend teaching students to only memorize the parts of words that do not follow learned phonics patterns.

At Reading Universe, we use three categories to describe high-frequency words: decodable, temporarily irregular, and irregular. Here's a more in-depth look into those three categories and what they mean for teaching:

Decodable high-frequency words, like at or can, are regularly spelled words, meaning that their sound-letter correspondences follow expected, predictable patterns. By learning the common patterns, students can sound out or decode these words.

Believe it or not, most high-frequency words introduced in kindergarten through third grade are actually decodable! These words can be grouped by spelling patterns and introduced when you teach that particular pattern. For example, as soon as students learn the sounds /ă/ and /t/, you can teach the word at.

Teacher Tip

About 85% of high-frequency words are fully decodable and follow regular phonetic patterns (Ehri, 1998; Miles, Eide, & Butler, 2024). With comprehensive phonics instruction, up to 99% of high-frequency words can be decoded using established phonetic rules. (Miles, Eide, & Butler, 2024)

To help students learn these decodable words by sight, you should:

Use them as examples when teaching the pattern (for example, use the high-frequency word must as an example when teaching ending blends)
Include them during dictation practice
Have students practice them repeatedly during activities and games

The word "for" with a heard over the "or"

Temporarily irregular high-frequency words contain regular sounds or spelling patterns that students haven't yet learned. They may seem like irregular words to students, and can be taught that way initially. But once students learn the spelling rules or patterns in the word, they find out that the word is actually decodable!

For instance, the word for is a common high-frequency word that students need to know early on to read connected text. While the word is decodable for students who have been taught the r-controlled vowel sound 'or', it is not decodable for students who have not yet had this explicit instruction.

The word "would" with a heart over "oul"

Irregular high-frequency words contain sounds or spelling patterns that do not follow typical phonics rules. These words often contain one or more unexpected spellings or tricky parts.

Let's look at the word would. The 'w' and the 'd' in would are decodable and make the sounds we expect them to make. The 'oul' part, on the other hand, makes an unexpected sound for those letters.

Teaching Irregular Words as Heart Words

Both temporarily irregular and irregular high-frequency words can be taught using the heart word methodology. Heart words, as we call them, each have a tricky part of the word that students must memorize, or learn "by heart." Some programs refer to these words as red words, trick words, or rule breakers.

The word "from" with a heart under the 'o'.

To teach a new heart word, you'll first have to determine which parts students can decode and which parts they cannot. The parts that don't follow regular phonics patterns, or that have patterns your students haven't learned, need to be memorized, or learned by heart. Once you and your students have analyzed the word, you can explicitly teach those tricky parts to help students remember the whole word.

Let's analyze the irregular word from. Students can decode the /f/, /r/, and /m/ sounds in the word. We can then explicitly teach them that the irregular part, 'o', which is making the /ŭ/ sound, is the part they'll need to learn by heart.

The word "play" with a heart under the 'ay'.

Similarly, when introducing the word play, students can easily decode the /p/ and /l/ sounds. However, if they haven't yet been taught the vowel team 'ay', they'll need to learn that part by heart.

Teacher Tip

When introducing heart words, plan to teach up to three heart words per week for kindergartners, and three to five words for students in grades 1-3.

Throughout the rest of this skill explainer, we will focus on how to teach both temporarily irregular and irregular high-frequency words. Since both types of words are taught as heart words using the same methodology, we'll sometimes just use the term irregular words to refer to both categories. In the chart below, you'll see these words are both under the umbrella of "words students can't decode."

Graphic showing high-frequency words are with words students can decode or words students can't decode, which are temporarily or always irregular.

So Then What Are Sight Words?

The terms high-frequency words and sight words are often used interchangeably, but they're not exactly the same. Here's the difference:

High-frequency words are the words that are commonly used in the English language and appear often in reading.
Sight words are words that students can recognize and recall instantly, without needing to sound them out.

As students learn and practice high-frequency words through explicit instruction, these words will become sight words. Sometimes we talk about the pool of words a student knows as their sight word bank or sight word vocabulary.

Words become sight words through a mental process called orthographic mapping. Through this process, the brain connects a word's pronunciation, spelling, and meaning. Supporting students in making these connections helps them store words in their long-term memory and promotes fluent reading.

The process goes like this:

Orthographic mapping graphic for the word "bed."

To support orthographic mapping, students need repeated and varied exposure to words, especially in meaningful context, to strengthen the connection between pronunciation, spelling, and meaning, and ultimately support long-term retention and fluency. This is especially important when teaching a group of high-frequency words that we call function words, which includes words like of, the, and was. Function words serve a grammatical role, but lack a clear, concrete definition, making them harder for students to visualize and store in memory.

The Dolch and Fry Word Lists

The Dolch Word List (opens in new window) and the Fry Word Lists are both commonly used collections of high-frequency words. The Dolch list includes 220 high-frequency words commonly found in texts for young children. The Fry list contains the 1,000 most common words in reading materials through ninth grade, organized into groups of 100. Many teachers use these word lists to help students develop automatic word recognition. Instead of having students memorize these words, it's more effective to group them by phonics patterns and teach them alongside your phonics instruction, introducing any truly irregular words as heart words through clear, explicit teaching.

1. An Overview of Irregularly Spelled High-Frequency Words

Irregularly Spelled High-Frequency Words Skill Explainer

Teacher Tip

Teacher Tip